Question: If $6a + b = -8$ and $4x + 9y + 3z = -5$, what is $36x + 81y - 24a - 4b + 27z$ ?
Answer: $= -24a - 4b + 36x + 81y + 27z$ $= (-4) \cdot (6a + b) + (9) \cdot (4x + 9y + 3z)$ $= (-4) \cdot (-8) + (9) \cdot (-5)$ $= 32 - 45$ $= -13$